The present invention is directed to an airspring having an airsleeve comprising an elastomeric liner; a reinforcing layer overlaying the liner; and a colorable elastomeric cover overlaying the reinforcing layer; the cover comprising: 100 parts by weight of elastomer comprising from about 30 to about 50 parts by weight of natural rubber, from about 10 to about 30 parts by weight of polybutadiene, and from about 30 to about 50 parts by weight of ethylene propylene diene terpolymer (EPDM); from about 20 to about 60 parts by weight, per 100 parts by weight of elastomer, of silica; and from about 1 to about 10 parts by weight, per 100 parts by weight of elastomer, of an organosilane polysulfide.
Airsprings have been used for motor vehicles and various machines and other equipment for a number of years. The springs are designed to support a suspension load such as a vehicle. The airspring usually includes a flexible elastomeric reinforced airsleeve that extends between a pair of end members. The airsleeve is attached to end members to form a pressurized chamber therein. The end members mount the airspring on spaced components, or parts of the vehicle or equipment, on which the airspring is to be mounted. The internal pressurized gas, usually air, absorbs most of the motion impressed upon or experienced by one of the spaced end members. The end members move inwards and towards each other when the spring is in jounce, and away and outwards from each other when the spring is in rebound. The design height of the airspring is a nominal position of the spring when the spring is in neither jounce nor rebound.
There have been two basic designs of airsprings: a rolling lobe airspring, as seen in U.S. Pat. Nos. 3,043,582 and 5,954,316; and a bellows type airspring, as seen in U.S. Pat. Nos. 2,999,681 and 3,084,952. In a rolling lobe-type airspring, the airsleeve is a single circular-shaped sleeve secured at both ends. During jounce, the airsleeve rolls down the sides of a piston support. In a bellows-type airspring, the multiple meniscus-shaped portions of the airsleeve extend out radially as the spring is in jounce.
Airsleeves have a rubber innerliner, two plies of rubber coated cord fabric, and a rubber cover. These sleeves see their greatest commercial usage in the automotive helper spring market by being mounted as airsprings on shock absorbers and struts. Other uses include truck cab suspension springs, truck driver seat springs, automobile airsprings, and a variety of industrial airsprings.
In the manufacture of fabric-reinforced, molded rubber articles such as airsleeves, it is desirable to obtain strong adhesion between the fabric plycoat and the cover, and also high resistance to deterioration of the bond with flexing of the structure.
Airsleeves are typically black, owing to the presence of carbon black as a reinforcement. In some applications, however, it may be desirable to have an airspring cover with a color other than black. Such a cover would be useful for purposes of identification and uniformity. The cover compound must, however, satisfy the requirements of flex and adhesion.
The present invention is directed to an airspring having an airsleeve comprising an elastomeric liner; a reinforcing layer overlaying the liner, and a colorable elastomeric cover overlaying the reinforcing layer, the cover comprising: 100 parts by weight of elastomer comprising from about 30 to about 50 parts by weight of natural rubber, from about 10 to about 30 parts by weight of polybutadiene, and from about 30 to about 50 parts by weight of ethylene propylene diene terpolymer (EPDM); from about 20 to about 60 parts by weight, per 100 parts by weight of elastomer, of silica; and from about 1 to about 10 parts by weight, per 100 parts by weight of elastomer, of an organosilane polysulfide.